1. Field of the Invention
The invention relates to a phacoemulsification apparatus that is used to control fluid flow transfer within a surgical site of an eye. The apparatus includes a needle whose outer surface converges and inner channel narrows.
2. Discussion of Related Art
A wide array of fluid-irrigated, ultrasonically-operated cutting devices have been developed for ophthalmological surgical techniques such as phacoemulsification--a method for removing a cataract through a surgical incision in the eye.
Heretofore, phacoemulsification involved the use of a dual chambered handpiece consisting of a hollow metallic needle surrounded by a tubular sleeve. The needle is vibrated ultrasonically at selected frequencies and amplitudes to fracture the cataract to be removed and replaced by an intraocular lens. The fractured cataract tissue is aspirated through the needle interior through the use of a suction force. A fluid is infused into the eye through the tubular sleeve to irrigate the eye. The tubular sleeve has been made heretofore preferably of a soft material such as silicone or less desirably of a rigid composition such as metal or teflon.
Phacoemulsification needles come in many different configurations. Some are straight yet their inner channel narrows in diameter in a direction heading away from the open tip and spaced therefrom. Some of these also have an outer surface that converges from the tip, with the inner channel narrowing in diameter for the length of this convergence. Still others are angulated and have an inner channel that is of constant diameter.
U.S. Pat. No. 5,084,009 ('009 patent), entitled FLUID INFUSION SLEEVE FOR USE DURING EYE SURGERY, which issued to Richard Mackool on Jan. 28, 1992, whose contents are incorporated herein by reference, discloses a silicone sleeve and discusses the problems that arise from the incision compressing the non-rigid, pliable silicone sleeve. Such problems include the sleeve collapsing on the vibrating needle so that the needle, which is being vibrated at ultrahigh frequencies, rubs against the sleeve and the irrigation flow path between the needle and the sleeve becoming constricted due to the collapsed sleeve.
The sleeve through which irrigation takes place, i.e., delivering fluid to the eye, should be made of soft material that can deform to match the contour of the eye incision and thereby prevent leakage. To prevent the sleeve from collapsing on the vibrating needle, the '009 patent suggests surrounding the needle with a rigid sleeve that is interposed between the needle and the outer, soft, silicone sleeve. Thus, a collapse of the outer, soft, silicone sleeve will be onto the rigid sleeve rather than in rubbing contact with the vibrating needle.
U.S. Pat. No. 5,505,693 ('693 Patent), entitled "Method and Apparatus For Reducing Friction and Heat Generation By an Ultrasonic Device During Surgery", which issued to Richard Mackool on Apr. 9, 1996 and whose contents are incorporated herein by reference, discloses a soft outer sleeve having a rigid lining, thereby obviating the need for a separate rigid sleeve between the outer sleeve and the needle.
The experience of the applicant, who has performed literally thousands of cataract eye operations, has found that during the course of an eye surgical operation, the tubes that lead to the handpiece of the phacoemulsification instrument from a surgical console are susceptible to unintentional kinking by medical personnel if the tubes are made from soft, pliable material that may elastically expand under pressure. These tubes include the infusion tube from the fluid supply to the handpiece and the discharge tube from the handpiece to the drainage receptacle or suction. There is no vibratory needle within these tubes so there is no risk of making unwanted rubbing contact as would prompt the solution of interposing a rigid sleeve to surround the needle as taught in the '009 patent.
Kinking may lead to severe consequences. If the infusion tube becomes kinked, a pressure loss downstream may lead to deflation of the eye. Such deflation could lead to collapse of certain eye tissues upon each other or upon the surgical instrument which extends into the eye. Either way, the tissues which are most likely to be damaged from such deflation are the cornea, the iris and the lens capsule, all surrounding the cataract. Fragile cells which line the inside of the cornea are known as corneal endothelium and they cannot be regenerated by the eye. Damage to the corneal endothelium can cause permanent damage to the cornea, resulting in a corneal clouding and decreased vision. A corneal transplant may then be necessary.
If the discharge tube becomes inadvertently kinked or, as commonly occurs, blocked by fractured tissue, the eye will still be pressurized, but the surgical operation will cease until the kink or blockage is eliminated. At the time of the kinking or blocking, however, the pressure falls downstream so that upon removal of the kink or blockage, a sudden surge in the outflow rate arises as the downstream vacuum acts to drain the eye due to loss of upstream pressure. This sudden drop in upstream pressure is felt by the eye, tending to create some deflation until normal flow is restored. It would be desirable to avoid such deflation by allowing the infusion tube to expand to hold more fluid and develop elastic energy which upon release can cause increase of flow into the eye and thereby counter the abrupt surge in the outflow upon removal of the kink or blockage. Soft material, such as silicone, elastically expands under pressure build-up and so its use is preferable.
Upon release of the blockage or kinking, the expanded, soft infusion tube contracts back to its unexpanded state and thereby provides a temporarily greater volume of fluid flow per second than was being supplied to the eye before the kinking or blocking arose. Thus, the volumetric loss of fluid during the sudden surge in outflow upon removal of the kink or blockage is better compensated by the larger volume of fluid readily available under pressure in the expanded, soft infusion tube.
U.S. Pat. No. 5,685,841 (the '841 patent) issued to Richard Mackool on Nov. 11, 1997, whose contents are incorporated herein by reference, offers a solution to the kinking problem.
The infusion sleeve may be circular or ellipsoidal in cross-section and is made of a soft, pliable material. Preferably, a rigid, noncompressible sleeve is surrounded by this infusion sleeve and acts as a barrier between the infusion sleeve and the needle in the event the infusion sleeve collapses, thereby preventing undesirable rubbing contact.
The '841 patent reveals a conventional phacoemulsification handpiece arranged to irrigate fluid into the eye and aspirate fluid and tissue from the eye continuously throughout an eye surgery operation. A concentric relationship exists between the needle, the rigid, noncompressible sleeve and the infusion sleeve. The forward end of the infusion sleeve is tapered. There is a vibratory drive in the handpiece for imparting vibratory motion on the hollow needle. The infusion sleeve defines a chamber between its inner wall and the outside of the vibrating hollow needle. Irrigation into the eye is provided normally through this chamber and aspiration from the eye is through the needle.
The irrigation is provided from a gravity fed fluid supply and through an infusion tube to the handpiece. Aspiration is provided through a discharge tube from the handpiece to a drain receptacle. In a known manner, a gate valve is provided to permit flow through the infusion tube to occur. The fluid supply is at a higher elevation than the eye. A pumping mechanism may be present and, when activated, suctions fluid from the eye and through discharge tube.
The tubes may be susceptible to unintentional kinking by medical personnel unless they are made from an incompressible material. If the kinking arises in the discharge tube, the surgical procedure stops but the eye remains inflated under pressure. If the kinking arises in the infusion tube, however, a pressure drop in the eye ensues that leads to its collapse. Such a collapse causes unwanted contact of eye tissue.
It may be desirable to form at least the infusion tube of a soft, elastic, expandable material such as silicone to counteract the momentary flow surge that eventually results if the outflow through the discharge tube becomes blocked, e.g., by tissue fragments. When such blockage arises, pressure decreases downstream to the blockage so that when the blockage is removed, there is a momentary surge in the outflow. Such a sudden event release tends to deflate the eye. To counter this deflation, the infusion tube could be made to expand under a build-up of pressure, as takes place during blockage of the outflow through the discharge tube. When the blockage is removed, the infusion tube would elastically compress back to its unexpanded state and thereby offset the momentary surge in the outflow.
U.S. Pat. No. 5,154,694 to Charles Kelman discloses a tissue scraper device for medical use for which the tip portion of the needle is angulated. Such an angulated needle is currently commercialized by Alcon Laboratories. The angulation on their product is 22.degree., the outer diameter of the needle varies between 1.1 and 0.9 mm, and the inner diameter between 0.9 and 0.6 mm. The distance between the angulation and the tip is approximately 4 mm. The tip has a distal port with an angulation which varies between 0.degree. (port perpendicular to the axis of the angulated portion of the tip) and 45.degree..
U.S. Pat. No. 3,589,363 to Banko and Kelman (the '363 patent) discloses a hand held instrument and method for breaking apart and removing by flushing fluid flow undesired material such as tissue from a body site. The instrument contains a vibratory drive connected to a longitudinal shank having an axial bore leading to a mouth at its projecting straight tip, and a conduit leading to an opening at the shank exterior, such that axial vibratory movement of the tip, when pressed axially against the tissue, breaks up the tissue by jack-hammer-like action, for removal by flow of fluid from a source to the site via one of the mouth and opening and its return with broken up tissue via the other of the mouth and opening to a suction source.
This '363 patent teaching covers break up and removal of cataracted eye lens tissue per known surgical procedures. Such procedures are effected through a corneal incision kept as small as possible to minimize patient trauma. In this regard, it is desirable to remove all tissue debris from the posterior capsule.
However, it has been found that in using the straight tip instrument for such purposes, the procedures are burdened by awkwardness in the positioning of the instrument in the surgeon's hand under the extant vibratory conditions, especially when attempting to break up portions of the cataracted lens tissue in remote portions of the posterior chamber in relation to the fixed position of the necessarily small corneal incision. This awkwardness leads to uncomfortable hand and finger positions of the surgeon when holding the vibrating instrument and manipulating it in relation to that fixed location of the corneal incision for bringing the free end of its straight tip into proper "head-on" position for breaking up the lens tissue in the inherently confined spatial areas involved.
While the instrument according to the '363 patent may be provided with a radially extending, sharp pointed projection, this is only used to tear the anterior wall of the capsule covering the lens by back and forth tearing action to obtain access to the lens prior to initiation of the tissue breaking apart procedure. This projection would be of no value in breaking apart the main mass of the lens tissue within its capsule, especially considering that the projection has a pointed end and is positioned with that end remote from the tip mouth through which the flushing fluid flows.
On the other hand, the back and forth jack-hammer-like action of the straight tip of the instrument of the '363 patent, which is used for the actual breaking up of the lens tissue, operates by way of axial or longitudinal direction percussion impulse exerted perpendicularly against the tissue surface as anvil, inherently resulting in a coarse shattering of the tissue.
As a result, the surgeon must take pains to manipulate the tip through many diverse angular positions, while the shank extends through the relatively small incision, to be able to apply the leading transverse face of the longitudinal straight tip in "head-on" relation with the lens tissue, as the very nature of the percussion impulse action is such that the axially vibrating tip makes head-on face-to-face contact with the tissue surface. Also, care must be taken to avoid unduly pressing the tip against the tissue surface of the posterior capsule for fear of puncturing or otherwise damaging unnecessarily that was which is intended to remain intact.
It is desired to configure the needle to enhance cavitational forces near the evacuation port, increase resistance to fluid out flow from the eye, reduce fluid surge, improve infusion capacity, widen tolerances for rigid sleeves and avoid the need for collars on the needle. Such collars are present on some straight needle designs, and act to restrain the rigid sleeve and prevent its forward migration toward the distal end of the needle.